Microprocessors

1
Microprocessors

• Chapter 2

2
The CPU Chip

• The term Microprocessor Chip and CPU mean the
  same thing.
• A CPU functions more like a powerful calculator
  than like a brain.
• CPUs really are not very smartjust very fast at
  manipulating groups of 0s and 1s.
• All of the data processed by a CPU is represented
  in terms of 0s and1s.

3
External Data Bus

• The external data bus (EDB) is the way the CPU
  communicates with the outside world.
• The state of a wire is expressed in a binary
  format, with 0s and 1s
• 1s represent a switch that is turned on and 0s
  represent a switch that is turned off.
• All data read into or out of the CPU must be
  represented in binary form.

4
Registers

• Inside the CPU there are four work areas called
  registers. we do not see these from the
  outside.
• These registers are areas used by the CPU to
  process data.
• The four general purpose registers found in all
  CPUs are AX, BX, CX, and DX.

5
Clock Speed

• CPU Manufacturers design their chips to operate
  at a specific speed such as 2 GHz.
• The motherboard clock speed is set by a component
  on the mother board called the system crystal.
• The system crystal is made of quartz-crystal
  material and will pulse at a known frequency when
  voltage is applied to the crystal.

6
The System Crystal

• The system crystal ultimately determines the
  speed at which a CPU and the motherboard bus
  operate.
• As long as the computer is turned on the quartz
  crystal oscillator pulses the CLK (clock) line on
  the motherboard.
• Each pulse is termed a clock cycle.
  

7
System Crystal

• The system crystal defines the speed at which the
  CPU and the rest of the PC operate
• Quartz oscillator, usually soldered to the
  motherboard
• Overheating results from overclocking the CPU
  (running it faster than its maximum clock speed)
  

8
Bad News about CPU speed

• The bad news is that when a manufacturer
  advertises the speed of a processor as 2GHz they
  are only telling you how fast the processor runs
  internally.
• Once data comes out of the CPU and travels on the
  motherboards bus the processing speed slows down
  to the speed of the motherboard bus.

9
Multipliers

• The speed at which the bus on a motherboard
  operates is directly determined by the system
  crystal.
• If the crystal is oscillating at 200 MHz then the
  motherboard bus speed is 200 MHz.
• The bus speed along with the multiplier setting
  determine the internal speed of the CPU.
  

10
Northbridge

• The memory controller chip (MCC) also called the
  Northbridge is a device that regulates the flow
  of data from the RAM to the CPU via the External
  Data Bus

11
Address Bus

• The address bus enables the CPU to control the
  Northbridge
• Another set of wires in addition to the external
  data bus
• Used by the CPU to tell the Northbridge which
  line of code it wants from RAM

12
Address Bus

• The number of wires in the address bus determines
  the maximum amount of RAM the CPU can address.
• If a CPU has 20 address lines the it can address
  220 combinations (1,048,576)
• Each number represents a different location in
  RAM
• 00000000000000000000 thru 11111111111111111111.
  

13
Terminology
14
Modern CPUs
15
Defining CPUs

• There are four main criteria used to describe and
  compare CPUs
• Make
• Intel, AMD, Cyrus
• Model
• 486DX2, Pentium, Pentium Pro, Athlon
• Speed
• Measured in MHz or GHz such as 266 MHz or 1.4 GHz
• How its mounted
• Slotted or socketed

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Common CPU Packages

• Staggered Pin Grid Array (SPGA)
• Pins are staggered and more closely packed to
  keep the overall size of the package small
• Pentium, Pentium Pro, K5, K6, 6x86

17
Common CPU Packages

• Single Edge Contact Cartridge (SECC) Take up less
  space and enable better cooling of the CPU.
  Obsolete Celeron, Pentium II, Pentium III,
  Athlon

18
Pentium CPU

• CPU makers have added a large number of
  improvements over the years
• Larger external data buses
• Larger address buses
• Faster clock speeds
• Intel introduced the Pentium CPU in the early
  1990s
• 32-bit registers
• Speeds up to 300 MHz
• Ability to run multiple programs at once
• Access super-fast cache RAM
• Processes two or more lines of code at the same
  time

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Multiprocessing

• Multiprocessing is running two programs at the
  same time
• Pentium processors have a 32-wire address bus
  that can address up to 232 or about four
  gigabytes of memory
• Actually CPUs do not run two programs at once.
  They simply switch back-and-forth between them so
  that it looks like they are doing two things at
  once.

20
Address Lines and RAM

• 16 address lines 65,536
• 20 address lines 1,048,576
• 24 address lines 16,777,216
• 32 address lines 4,294,967,296
• 36 address lines 68,719,476,736

21
Cache

• Cache means to set aside data in a special, fast
  storage area
• Disk cache is moving data between mass storage
  and RAM
• RAM cache is moving data between RAM and the CPU
  

22
DRAM

• DRAM (Dynamic RAM) is cheap, small, and
  relatively fast
• Each storage bit is a microscopic capacitor and
  transistor
• The capacitor holds a charge for about 16
  milliseconds and then discharges it.

23
DRAM

• To prevent loss of data added to DRAM, a process
  called refresh is used to recharge the capacitors
• Data added to RAM will disappear after 16
  milliseconds if not recharged, which is why DRAM
  is considered volatile RAM
• A wait state is created when the CPU tries to
  access the RAM when it is being refreshed
  

24
SRAM

• SRAM (static RAM) is a type of RAM that uses
  special circuits called flip-flops instead of
  capacitors that do not need to be refreshed
• About ten times more expensive than DRAM.
  

25
External Cache

• An external cache is also known as L2 cache
• The size of the cache varies from 64K to 1MB
  

26
Clock Doubling

• Clock doubling is used to enhance the CPU speed
• Running the internals of a CPU at one speed, and
  the external data bus at another slower speed
• All CPUs use multipliers
• Pentiums use variable multipliers

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Dual Pipeline

• A pipeline is a series of steps taken by the CPU
  to process a command
• Dual pipelining is the process of processing more
  than one command at a time through the use of
  separate sets of circuitry
• Dual pipelining in a Pentium is achieved through
  the U (main pipeline that can do anything) and V
  pipeline (handles only simple commands)
  

28
CPU Voltages

• The Pentium 60 and 66 MHz needed 5 volts for
  operations, whereas later Pentiums operated on
  3.3 volts only
• A CPU can run on a lower voltage by reducing
  transistor size, thereby reducing the overall
  size of the chip
• The voltage regulator module (VRM) is a small
  card that enables a CPU to standardize voltage
  regulators

29
The Pentium CPU

• The first Pentium processor (1993) had a 64-bit
  external data bus that was split internally as
  two dual-pipelined 32-bit data buses
• Enabled the CPU to process two separate lines of
  code simultaneously
• Capable of branch prediction allowing the CPU to
  anticipate program branches
  

30
Clock Doubling

• Pentium CPUs do not have built-in multipliers
  (clock doubling or more to run the internals of a
  CPU faster than the external data bus)
• Set with the help of jumpers or switches present
  in the motherboard
• Clock speed and multiplier can be adjusted via
  the CMOS setup program

31
Pentium Socket Types

• Most Pentium processors use the Staggered Pin
  Grid Array (SPGA) package
• Enables higher pin density and smaller case
• Socket 5 and Socket 7 were the two standard
  sockets for lower-powered Pentiums
  

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Pentium Pro

• Pentium Pro is also known as the P6
• Bus and register size is similar to Pentium
• Quad pipelining
• Pentium was dual-pipelined and could only run two
  processes simultaneously
• Dynamic processing
• While waiting for information from DRAM, the CPU
  could process other commands
• On-chip L2 cache

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Bus Types

• Frontside bus
• Address bus and external data bus are combined
  together between the CPU, MCC, and RAM
• Backside bus
• Connection between the CPU and L2 cache
• Remember that L2 cache used to be external cache
  but is now internal to the CPU housing

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Pentium Class CPUs

• MMX (Multimedia Extensions)
• Designed for graphical applications
• All new CPUs have MMX enabled
• Split voltage
• Two different voltages are required for different
  chips on the motherboard
• Super Socket 7 motherboards required
• Increased clocks and multipliers
• Improved processing
• Pentium II
• Faster Pentium Pro with MMX

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Pentium Class CPUs

• AMD K6 series
• Requires a Super Socket 7 motherboard
• K6, K6-2, K6-2, K6-III
• Celeron
• Offshoot of Pentium IIs for the low-end PC
• Pentium III
• Intels answer to 3DNow! by AMD

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Pentium Competitors

• AMD Athlon
• 9 pipelines, dynamic branch prediction, 200 or
  266 MHz system bus
• CPU and chipset perform two calculations on every
  clock cycle
• Must use a motherboard with Slot A
• AMD Duron
• AMDs competitor to Intels Celeron for the
  low-end PC

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Mobile Processors

• Mobile processors
• For laptops
• Overcome the problems of heat and size

38
More Processors

• Intel Xeon processors
• Series of powerful Slot 1 CPUs
• Massive L2 caches
• Intel Pentium 4
• 20-step pipeline that enhances its
  core processing function
• Four data transfers per clock cycle
• AMD Athlon XP
• Enhanced version of the Athlon core processor

39
64-Bit Processors

• 64-bit processing refers to a 64-bit address bus
• We already had 64-bit external data buses
• Intel Itanium processors
• Itanium was Intels first 64-bit chip
• Itanium II is made for the PC
• AMD Opteron processor
• Runs both 32-bit and 64-bit code

40
Mobile Processors

• Laptops require CPUs that are smaller, use less
  power, and run cooler
• AMD and Intel make mobile versions of all of
  their CPUs
• Intel introduced the mobile module that includes
  the processor and support chips to conserve space
• System Management Mode (SMM) is used to reduce
  power consumption on laptops

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Intel Pentium 4 Page 69

• A seventh generation of CPU from Intel
• More powerful core processing
• Enhanced graphics
• 400 MHZ system bus 4 data transfers per clock
  cycle
• In 2002 Intel introduced a quad pumped Pentium
  with an 800 MHZ frontside bus.
  

42
Pentium 4 Package

• Two classes of Pentium 4 pagkages
• 423-pin PGA package with 256 KB of L2 cache
  memory.
• 478-pin PGA package with 512 KB of L2 cache
  memory.
• External bus speed of 100 and 133 MHz
• Uses sockets 423 and 478 depending on model
• Multiplier range of x13 to x23
• Internal speed 1.3 GHz to 3.4 GHz

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AMD Athlon XP

• 462 pin PGA package
• Uses a Socket A
• Cache sizes
• L1 128 KB
• L2 256 KB
• External bus speed 133 - 166 MHz
• Multiplier range x13 to x16.5

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Installing CPUs
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Why Replace a CPU?

• Cost
• Chances are youll need to replace the
  motherboard as well as the CPU is it worth it?
• Cooling
• Faster CPUs will probably need better cooling
• Performance
• Faster CPUs may not be the best answer to
  speeding up your PC
• Many times what you really need is more RAM
  

46
The Right CPU

• Consult your motherboard manual
• You need a CPU that will fit in the socket or
  slot you have on your motherboard
• Buying a CPU
• Most stores will not accept returns
• Retail-boxed CPUs are genuine and come with a fan
• There are a lot of illegal CPUs on the market

47
CPU Installation Guidelines

• Dont touch the pins
• Match the notch and dot printed on the corners of
  the CPUit must line up
• Incorrectly installing your CPU may destroy the
  CPU and/or motherboard!

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CPU Installation Guidelines

• Install a fan on top of the CPU after the CPU has
  been inserted into the socket
• Use a heat sink compound

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Plugging in the CPU Fan
50
Inserting a Slot I / Slot A CPU

• Install the CPU mount
• Usually requires removing the motherboard
• Add a small amount of heat sink compound before
  mounting the fan
• Slide the CPU straight down notches will make
  it impossible to install incorrectly
• Plug in the CPU fans power

51
Inserting a Slot 1/ Slot A CPU
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The Art of Cooling

• Modern CPUs need to be kept cool
• OEM fans are included in retail-boxed CPUs
• Liquid cooling works by running a liquid (usually
  water) through a metal block that sits on top of
  your CPU to absorb heat